G-audeistzio dalla zonca



UNITED STATES PATENT OFFICE.

GAUDENZIO DALLA ZQNOA, OF VENICE, ITALY.

PROCESS OF TANNING.

SPECIFICATION forming part of Letters Patent No. 240,493, dated April 19, 1881. Application filedAugust 17, 1880. (No model.) Patented in France'July 2, 1880.

from the pit or vat. The bags are again emptied To all whom it may concern:

of liquor after the lapse of another hour and Be it known that 'I, GAUDENZIO/DALLA ZONCA, leather merchant, of Venice, Ital y, have invented a new and Improved Process of Tanning Hides and Skins, (for which I have received Letters Patent of France, dated July 2, 1880 and I dohereby declare that the following is a full, clear, and exactdescription of the same.

This invention has for its object to reduce the time required for tanning hides and skins with the ordinary vegetable matters, and without having recourse to chemical substances which injure their quality.

0 this end the hides, after undergoing the depilatory operation, say to the number of one hundred and seventy-five pieces, weighing (dry) about four hundred kilograms, are placed in a number of casks, together with about one hundred and thirty kilos of ground fir-bark, which is distributed among the several casks, according to the weight of the hides contained in each. The casks with the hides are then immersed in an infusion of the same bark, in which the casks are rotated for about twelve hours by steam-power, and after this the hides are taken out and drained. By this first operation the desired color is obtained. The hides are then sewed together in pairs to form bags, with the hair side outward, leaving an opening either at the end corresponding to the head of the animal, or at any other point, such as at one of the legs, for example, at which to introduce a mixture of oak-bark, nut-galls, and fir-bark in powder in the proportion of in this case the contents of the vat are slightly heated by means of a small furnace in communication with the vat. The same operation is repeated five times at intervals of two hours, the temperature of the liquor being raised to a higher degree each time until the hand can hardly bear the heat. The bags require to be shaken from time to timethroughout the whole operation, in order that the tanning principle of the contents may be developed and caused to act uniformly.

After the above operations are terminated the bags are emptied of the liquor they contain and laid at the bottom of the vat for the next twelve hours. Another batch of hides is at the same time laid upon those in the vat and treated as above described. The first batch of hides is withdrawn at the end of the twelve hours and the bags unstitched. The hides will then be perfectly tanned; but in order that-they should not lose in weight they are again placed in the casks and rotated for about fort eight hours in a solution of three hundred kilos of oak-bark and one hundred kilos of fir-bark for ever 1 one hundred andseventy-five pieces, weighing four hundred kilos in a dry state. The tanning operation is thereby not only improved, but the loss in weight is reduced to a minimum.

The above process is that employed for light skins, but it equally applies to hides used for sole-leather, except that after having divided them in the usual manner they are piled one gram of hide (dry.) For one hundred and seventy-five hides, weighingfour hundred kilograms when dry, I employ about eleven hundred kilograms of oak-bark, one hundred and ten kilograms of nut-galls, and two hundred and fifty kilograms offir-bark. I then put the bags in a pitorlarge' vat about half tilled with an infusion or decootion of the same substances, which may be used without changing for about ten or twelve days. The bags are then filled up with the cold liquor, the mouths closed by being twisted and tied tightly. They are then laid horizontally in the pit or vat, where they remain half covered with liquor. The liquor is removed from the bags after the lapse of an hour, and they are again filled up with liquor one and aquarter kilogram per kilogram ofskin At the end of thirty-eight days the hides, if of medium weight, will be thirty-five days, when they will be thoroughly tanned.

By means of the above process light skins weighing about one and three-quarter kilogram may be tanned in three days, instead of requiring from four to five months, as in ordinary tanning, while hides weighing from three to four kilograms occupy but six days, instead of five to six mon'thsby the old process. Heavy hides are perfectly tanned in from forty to seventy days, whereas hitherto they have required from six to seven or from eight to ten months, according to their thickness, to obtain the same results.

The substances specified in the process before described are those which I prefer to employ; but other substances may be used in lieu thereof, such as common valonia, catechu, extract of chestnut, Muller tannin, myrobolans, or any other vegetable substances possessing sufficient tanning power and capable of affording the same results. Another advantage is that a gain of upward of ten per cent. in weight is obtained as compared with the ordinary processes.

I do not claim making hides into bags and filling and surrounding them with tanningliquid; nor the use of heated tanning-solution; nor any of the steps which together constitute my process by itself.

I claim- The process herein described of tannin ghides and skins by exposing them, first, to contact with dry or ground fir-bark, then immersing them in an infusion of fir-bark, then sewing them into bags and filling said bags with a mixture of dry or ground oak-bark, nut-galls, and fir-bark in substantially the proportions stated, then immersing them with the same kind of mixture, and from time to time increasing the heat of said mixture, so that it will at intervals be hotter than before, and renewin g the same, substantially as specified.

GAUDENZIO DALLA ZONOA.

Witnesses:

GUST. CAREER, G. NoBERossA. 

